For me first impression is very important. When I visit the website of the project and it looks promising judging on the effort they put on the design and information available, that is already 1 point for me. Then, I will check the uniqueness of the project, if some altcoins already have the feature, it is a no no for me but if it is unique or we can say an improve one then I need to check first the whitepaper. This is the most important part, detailed information of the project should provide in the whitepaper. These things what I consider when choosing a new altcoin.